42 lines
1.0 KiB
C++
42 lines
1.0 KiB
C++
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#include "interrupt/timer.h"
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#include "common/port.h"
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namespace {
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// IO Ports
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constexpr uint8_t kPit0Ctl = 0x40;
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constexpr uint8_t kPit1Ctl = 0x41;
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constexpr uint8_t kPit2Ctl = 0x42;
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constexpr uint8_t kPitCmd = 0x43;
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// Command Register
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// Mode
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constexpr uint8_t kPitMode0 = 0x00;
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constexpr uint8_t kPitMode1 = 0x02;
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constexpr uint8_t kPitMode2 = 0x04;
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constexpr uint8_t kPitMode3 = 0x06;
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constexpr uint8_t kPitMode4 = 0x08;
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constexpr uint8_t kPitMode5 = 0x0A;
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// R/W
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constexpr uint8_t kCmdLatch = 0x00;
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constexpr uint8_t kCmdRwLow = 0x10;
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constexpr uint8_t kCmdRwHi = 0x20;
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constexpr uint8_t kCmdRwBoth = 0x30;
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// PIT Select
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constexpr uint8_t kSelect0 = 0x00;
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constexpr uint8_t kSelect1 = 0x40;
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constexpr uint8_t kSelect2 = 0x80;
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constexpr uint8_t kReadback = 0xC0;
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constexpr uint32_t kPitFrequency = 1193182;
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} // namespace
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void SetFrequency(uint64_t hertz) {
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uint16_t reload = kPitFrequency / hertz;
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outb(kPitCmd, kPitMode3 | kCmdRwBoth | kSelect0);
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outb(kPit0Ctl, reload & 0xFF);
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outb(kPit0Ctl, reload >> 8);
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}
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